JP4250793B2 - Piezoelectric actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a piezoelectric actuator, and more specifically, has a structure in which the contact member and the driven body are relatively moved by transmitting vibration excited by the piezoelectric element to the driven body through the contact member. In the piezoelectric actuator, the frictional force of the contact part that becomes the driving force transmission part is increased to improve the driving force transmission efficiency, and further the wear resistance of the contact part is enhanced and the occurrence of microcracks and peeling is suppressed, resulting in durability. In particular, the present invention is effectively applied to a truss-type piezoelectric actuator.
[0002]
[Prior art]
As a typical piezoelectric actuator, for example, a truss-type piezoelectric actuator having a structure as shown in FIG. 1 is known. That is, in FIG. 1, 1a and 1b are piezoelectric elements, Va and Vb are AC power sources, 2 is a contact member (chip), 3 is a base member, 4 is a biasing member, 5 is a fixed portion, and 6 is a driven body. Show. A contact member (chip) 2 is fixed to the ends of the two piezoelectric elements 1a and 1b arranged in a truss shape, and the other end is fixed to the base member 3. The base member 3 is biased by a spring or the like. It is fixed to the fixing part 5 via the member 4.
[0003]
When two piezoelectric elements 1a and 1b are arranged at an angle of 90 °, for example, and an AC voltage having a phase difference of 90 ° is applied from the AC power supply Va and Vb to the piezoelectric elements 1a and 1b as shown in the drawing, The tip of the contact member (chip) 2 causes a circular motion (perfect circle or elliptical motion) due to vibration having a phase difference of 1a and 1b. Accordingly, the AC voltage having a phase difference between the piezoelectric elements 1a and 1b in a state where the base member 3 is fixed to the fixing portion 5 via the biasing member 4 and the contact member 2 is brought into frictional contact with the driven body 6 as shown in the drawing. Is applied, the driven body 6 generates a driving force in the direction of the arrow in the drawing due to the contact frictional force of the contact member 2 along with the circular movement of the contact member 2.
[0004]
In the illustrated example, the driven body 6 has a disc shape. However, the shape and structure of the driven body 6 are not limited to this, and other than the disc shape, an arc shape, a flat plate However, the operating mechanism is essentially unchanged.
[0005]
At this time, in order to drive the driven body 6 stably, it is necessary to increase the frictional force between the contact member 2 and the driven body 6 and to maintain a stable frictional force. In order to achieve this, the surfaces of the contact member 2 and the driven body 6 must have excellent wear resistance.
[0006]
Another advantage of increasing the wear resistance of the contact portion is that the generation of wear powder is suppressed, so there is no risk of malfunction by reducing the generation amount of wear powder, and the wear powder acts as an abrasive and wear. Furthermore, the problem of acceleration can be avoided.
[0007]
On the other hand, the rotational speed of the circular motion generated at the tip of the contact member 2 is a high frequency (about 100 to 200 kHz), and the contact member 2 and the driven body 6 repeat contact / non-contact in a very short cycle. Sometimes an impact force is repeatedly applied between the contact member 2 and the driven body 6.
[0008]
Accordingly, in order to continuously and stably exert the driving force of the piezoelectric actuator, it is extremely important to improve the frictional force and wear resistance of the contact member 2 and the driven body 6 constituting the contact portion.
[0009]
In addition, the wear resistance required for such a contact portion is not limited to the truss type piezoelectric actuator as shown in the figure. In short, all types of piezoelectric actuators that transmit the expansion / contraction vibration of the piezoelectric element to the driven body are used. It becomes an important requirement characteristic in common.
[0010]
As a method for increasing the wear resistance of the contact portion, a method for increasing the surface hardness of the contact member and the driven body is effective, and a specific method for increasing the surface hardness is a surface hardening treatment method. And when using the iron base metal base material with comparatively low hardness as a contact member or a to-be-driven body, the method of forming the thin film of several to dozens of micrometers which consists of a high hardness ceramic material on the base material surface is illustrated. .
[0011]
However, when a high-hardness wear-resistant thin film is formed on the surface of a low-hardness iron-based metal base material, etc., the base material and the hardened surface layer are said to be in the middle state (the interior is soft and the surroundings are thin and hard The structure is a state of being encapsulated with a film. And, as a result of various studies conducted by the present inventors, when a repeated impact force as described above is applied to the surface of a member having such a structure, the surface hardened layer easily causes microcracks and peeling. When this occurs, the wear of the contact portion proceeds rapidly, and a stable drive transmission force cannot be obtained.
[0012]
[Problems to be solved by the invention]
The present invention has been made paying attention to the problems of the prior art as described above, and its purpose is to transmit vibration excited by the piezoelectric element to the driven body via the contact member. Targeting piezoelectric actuators of the type that move the member and the driven body relative to each other, the frictional force of the contact portion serving as the drive force transmission portion is increased to further improve the drive force transmission efficiency and The purpose is to establish a technology capable of further improving the durability and reliability of the piezoelectric actuator by increasing the wearability and suppressing the occurrence of microcracks and peeling.
[0013]
[Means for Solving the Problems]
The piezoelectric actuator of the present invention that has solved the above-mentioned problem is that a contact member provided at the tip of a piezoelectric element is brought into contact with a driven body, and vibration or rotational force excited by the piezoelectric element is passed through the contact member. In the piezoelectric actuator that relatively moves the contact member and the driven body by transmitting to the driven body, the contact surface of the contact member and / or the driven body (surface) has a cushioning property. The contact member and the driven body are made of an iron-based metal base material, and the composite layer includes carbon, oxygen, sulfur, nitrogen, boron, tungsten, vanadium, titanium, niobium and the iron-based metal. The gist is that the hard layer has a multilayer structure or a hardness gradient structure including at least one element selected from the group consisting of chromium .
[0014]
The piezoelectric actuator of the present invention that has solved the above-mentioned problem is that a contact member provided at the tip of a piezoelectric element is brought into contact with a driven body, and vibration or rotational force excited by the piezoelectric element is passed through the contact member. In the piezoelectric actuator that relatively moves the contact member and the driven body by transmitting to the driven body, the contact surface of the contact member and / or the driven body is configured by a composite layer having a cushioning property. The composite layer is composed of a chromium carbide-containing layer formed on the surface of the iron-based metal base material and a vanadium carbide-containing layer formed thereon. As a more specific example recommended, the chromium carbide-containing layer can be easily formed by subjecting the surface of the iron-based metal base material to chromizing treatment or salt bath treatment, and the vanadium carbide-containing layer is It can be easily formed by subjecting the surface of the chromium carbide-containing layer to a salt bath treatment .
[0015]
The piezoelectric actuator of the present invention that has solved the above-mentioned problem is that a contact member provided at the tip of a piezoelectric element is brought into contact with a driven body, and vibration or rotational force excited by the piezoelectric element is passed through the contact member. In the piezoelectric actuator that relatively moves the contact member and the driven body by transmitting to the driven body, the contact surface of the contact member and / or the driven body is configured by a composite layer having a cushioning property. The composite layer is composed of a TiCN-containing layer formed on the surface of the iron-based metal base material, and the TiCN-containing layer is composed of a TiC rich layer, a TiCN rich layer, and a TiN rich layer from the base material side. Summary there Ru to. The recommended, a more specific example, the TiCN-containing layer, TiC-rich layer from the base material side, TiCN rich layer, there are such as those constituted by TiN rich layer, the composite layer of this type, Each layer constituent material can be easily formed by sequentially forming by a CVD method or the like .
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
As described above, in the present invention, the contact member between the contact member and the driven body constituting the driving force transmission unit in the piezoelectric actuator, in other words, the structure of the surface layer part where the contact member and the driven body contact, The surface layer has a multi-layer structure and cushioning characteristics. With these devices, the impact force applied to the outermost layer when the actuator is operating is absorbed and relaxed. Such as cracks and delamination).
[0017]
Therefore, the overall structure of the piezoelectric actuator according to the present invention is not essentially different from that shown in FIG. 1 or the like shown as the prior art, and a known piezoelectric actuator other than the truss type as shown in FIG. The above technical idea is effectively utilized.
[0018]
By the way, the surface of the contact member and the driven body in the conventional piezoelectric actuator has a thickness made of ceramics or the like on the surface of the base material B as shown in the conceptual diagram of FIG. 2 for the purpose of improving the wear resistance as described above. A surface hardened layer H of about several to several tens of μm is formed to have an intermediate structure. In such a structure, the base material B is insufficient in hardness as compared with the surface hardened layer H, so that it can be used during operation. The surface hardened layer H undergoes micro-cracks or delamination due to repeated impact force, and wear dust generated by the delamination acts as abrasive powder, which further accelerates wear. The frictional force (and hence drive transmission force) cannot be maintained for a long time.
[0019]
On the other hand, in the present invention, for example, as shown in FIG. 3, a composite layer in which an intermediate layer M is provided between a hardened surface layer H and a base material B constituting a contact surface is formed. The impact force of the hardened layer H is absorbed, and the occurrence of microcracks and delamination on the surface hardened layer H is suppressed.
[0020]
In order to effectively exhibit the cushioning action of such an intermediate layer, as a constituent material of the intermediate layer M, a material having hardness between the base material B and the surface hardened layer H and capable of absorbing and relaxing the impact force sequentially from the outermost layer side. More preferably, it is desirable to select a material having excellent adhesion to both the base material B and the surface hardened layer H and having a higher toughness than the base material B. Examples of the composite layer having such a structure include a composite phase in which a chromium carbide-containing layer is formed as an intermediate layer M on the surface of the iron-based metal base material B, and a vanadium carbide-containing layer is formed as a surface hardened layer H on the surface. The
[0021]
Next, FIG. 4 shows an example in which the impact force is absorbed and relaxed by forming the intermediate layer M as a two-layer structure of M1 and M2 and using them as a cushion layer having a composite structure as a whole. In this way, it is recommended as a more preferable embodiment that the intermediate layer M is formed in two layers (or three or more layers) to further enhance the impact absorbing effect.
[0022]
Further, FIG. 4 shows an example in which the intermediate layer M has a multi-layer structure and the hardness difference is provided in stages. However, the intermediate layer M has a single-layer structure, and gradually increases in hardness toward the surface layer side in the intermediate layer M. Also by providing such a hardness gradient, the impact absorption relaxation effect is effectively exhibited.
[0023]
A suitable material for such an intermediate layer M varies depending on the material of the base material B and the surface hardened layer H, and thus cannot be determined uniformly. However, the most common iron-based metal base material as a contact member or driven body , A curable element such as carbon, oxygen, sulfur, nitrogen, boron, tungsten, vanadium, titanium, niobium, or chromium is diffused and infiltrated into the surface of the iron-based metal base material by an ion implantation method or the like. The method of changing the type and amount of intruding elements and giving a hardness gradient that maximizes the hardness of the outermost layer side is preferably adopted. Of course, it is also possible to form a hardness gradient in the surface direction by sequentially applying a hard material by adopting a PVD method, a sputtering method or the like.
[0024]
The preferred shock absorption mitigation structure and its formation method when modifying a contact member or driven body made of an iron-based metal base material will be described in more detail as follows.
[0025]
One of them is a structure in which a CrC (chromium carbide) -containing layer is formed as an intermediate layer M on the surface of a base material B made of carbon steel, and a VC (vanadium carbide) -containing layer is formed thereon as a surface hardened layer H ( This is a specific example of FIG. Since the Cr-C-containing layer has higher hardness than carbon steel but lower hardness than the VC-containing layer, the CrC-containing layer acts as a cushioning material for the VC-containing layer constituting the outermost surface hardened layer H, Suppresses generation of microcracks and peeling in the high hardness VC-containing layer. In other words, since the VC-containing layer originally has high hardness and excellent wear resistance, the overall wear resistance is remarkably improved in combination with the impact absorbing action by the cushioning action of the CrC-containing layer existing as the intermediate layer M. It is done.
[0026]
Moreover, Cr is more easily diffused and penetrated into Fe than V, and the degree of diffusion into the iron-based metal base material is large. Therefore, the adhesion of the CrC-containing layer to the base material is also good. By forming the layer M as a layer, the peel strength of the surface hardened layer H made of the VC-containing layer is also increased, and in combination, the wear resistance of the surface hardened layer H forming material (contact member and / or driven body). Sex will be dramatically improved. Furthermore, the hard VC-containing layer at the outermost surface constituting the contact friction surface tends to have a rather high friction coefficient by being supported by a slightly lower CrC-containing layer (intermediate layer M). Drive transmission efficiency is also increased.
[0027]
A method for forming a composite layer composed of the CrC-containing layer and the VC-containing layer is not particularly limited, but a preferred method is as follows.
[0028]
As a base material, an iron-based metal (usually carbon steel represented by SKD11) having a carbon content of 0.8% by weight or more is used, and the chromizing treatment or salt solution treatment (TD treatment) is first performed on the surface. After forming a CrC-containing layer on the surface of the base material, a salt bath treatment (TD treatment) is further performed to form a VC-containing layer on the CrC-containing layer. As processing conditions at this time, general chromizing processing and salty processing conditions may be applied as they are or after being appropriately changed. The total thickness of the composite layer is suitably in the range of about 5 μm to several tens of μm from the viewpoint of ensuring sufficient wear resistance while maintaining an appropriate friction coefficient, and it is economically wasteful to make it excessively thick. In addition to this, there is a risk of lowering the coefficient of friction and lowering the power transmission efficiency.
[0029]
Another preferred composite layer belongs to the three-layer laminated structure as shown in FIG. 4, and has relatively good adhesion to the base material on the surface of the iron base alloy base material made of carbon steel or the like. A TiC-containing layer is formed as the intermediate layer M1, and a composite layer having a three-layer structure in which a TiCN-containing layer is formed on the surface of the TiC-containing layer and a hard TiN-containing layer constituting the outermost hardened layer is formed thereon.
[0030]
When TiC and TiN contained in this composite layer are compared, the hardness of TiC is greater and the toughness of TiN is better. TiN is considerably harder than the base material (carbon steel) and has excellent wear resistance, but the adhesion of the base material to the carbon steel (SKDll etc.) is inferior to TiC. Accordingly, a TiC-containing layer having good adhesion to the base material and having a high hardness is formed on the surface of the base material, and excellent adhesion to both the TiC-containing layer and the TiN-containing layer is exhibited on the TiC-containing layer. After the TiCN-containing layer is formed, a highly hard and tough TiN-containing layer is formed in the outermost layer. The composite layer having such a laminated structure is generally about 5 to 15 μm, more generally about 10 μm in total thickness, and the composite layer having such a thickness has an overall hardness of TiC. It is comparable to the single-containing layer and exhibits higher hardness than the single TiN-containing layer. In other words, the composite layer exhibits high toughness while maintaining extremely high hardness as a whole, and maintains micro-cracks and delamination due to repeated impacts when driving a piezoelectric actuator while maintaining a high level of friction coefficient and wear resistance. Occurrence is suppressed as much as possible, and as a result, a high level drive transmission force can be stably maintained.
[0031]
Such a composite layer having a three-layer structure can be easily obtained by, for example, a method of sequentially forming a TiC-containing layer, a TiCN-containing layer, and a TiN-containing layer on a carbon steel surface by a CVD method or the like. This method may be adopted. If the CVD method is adopted, a surface hardened film having the above three-layer structure can be formed, and a composite layer composed of a TiCN-containing layer having a hardness gradient structure in which the C and N concentrations are continuously changed as necessary. Is also easy.
[0032]
In this specification, the case where a composite layer with improved wear resistance is formed on the surface of the iron-based metal base material has been mainly described, but the constituent materials of the contact member and the driven body are of course the iron-based metal base material. Depending on the application, it is possible to select non-ferrous metals such as aluminum-based alloys as the base material, depending on the application, and the intermediate layer and surface hardening constituting the composite film can be selected accordingly. Although the preferred material of the layer varies, the main point is that when a hard wear-resistant film is formed on the surface of the base material, the overall wear resistance of the composite structure shows a cushioning action with excellent adhesion to the base material. Any film having a conductive film is included in the technical scope of the present invention.
[0033]
【The invention's effect】
The present invention is configured as described above, and the following effects can be obtained.
[0034]
(1) By increasing the cushioning property of the hardened surface layer, a stable frictional force can be obtained, and the controllability of the actuator is enhanced and the life is extended.
[0035]
(2) The impact strength can be absorbed and reduced by using a composite film with cushioning properties, microcracks and peeling of the hardened surface layer can be suppressed, the generation of wear powder can be reduced, and there is no risk of malfunction and durability. A highly reliable and reliable piezoelectric actuator can be provided.
[0036]
(3) Since the surface layer has excellent wear resistance, it is not necessary to use a lubricating oil, and a large frictional force can be obtained. Therefore, a large actuator driving force can be obtained.
[0037]
(4) The composite film can be formed by an inexpensive process such as salt bath treatment (chromium carbide, vanadium carbide), VC (vanadium carbide), chromizing treatment (chromium carbide), CVD treatment (TiCN, etc.). There is little burden.
[Brief description of the drawings]
FIG. 1 is an explanatory view illustrating the structure of a truss-type piezoelectric actuator.
FIG. 2 is a conceptual cross-sectional view illustrating a conventional surface structure applied to a contact member and a driven body.
FIG. 3 is a conceptual cross-sectional view illustrating the surface structure of a contact member or a driven body applied to a piezoelectric actuator according to the present invention.
FIG. 4 is a conceptual cross-sectional view illustrating the surface structure of a contact member or a driven body applied to another piezoelectric actuator according to the present invention.
[Explanation of symbols]
1a, 1b Piezoelectric element 2 Contact member (chip)
3 Base member 4 Biasing member (spring)
5 fixed part 6 driven body

Claims (5)

A contact member provided at the tip of the piezoelectric element is brought into contact with the driven body, and vibration or rotational force excited by the piezoelectric element is transmitted to the driven body through the contact member, whereby the contact member and the driven body are driven. In the piezoelectric actuator for relatively moving the body, the contact surface of the contact member and / or the driven body is constituted by a composite layer having a cushioning property, and the contact member and the driven body are made of an iron-based metal base material. And the composite layer has a multilayer structure or hardness containing at least one element selected from the group consisting of carbon, oxygen, sulfur, nitrogen, boron, tungsten, vanadium, titanium, niobium, and chromium in the iron-based metal. A piezoelectric actuator comprising a hard layer having an inclined structure . A contact member provided at the tip of the piezoelectric element is brought into contact with the driven body, and vibration or rotational force excited by the piezoelectric element is transmitted to the driven body through the contact member, whereby the contact member and the driven body are driven. In the piezoelectric actuator for relatively moving the body, the contact surface of the contact member and / or the driven body is constituted by a composite layer having a cushioning property, and the composite layer is formed on the surface of the iron-based metal base material. And a vanadium carbide-containing layer formed on the chromium-carbide-containing layer . The chromium carbide-containing layer is formed by chromizing or salt bathing the surface of the iron-based metal base material, and the vanadium carbide-containing layer is formed by salt bathing the surface of the chromium carbide-containing layer. The piezoelectric actuator according to claim 2 , wherein A contact member provided at the tip of the piezoelectric element is brought into contact with the driven body, and vibration or rotational force excited by the piezoelectric element is transmitted to the driven body through the contact member, whereby the contact member and the driven body are driven. In the piezoelectric actuator for relatively moving the body, the contact surface of the contact member and / or the driven body is constituted by a composite layer having a cushioning property, and the composite layer is formed on the surface of the iron-based metal base material. A piezoelectric actuator comprising: a TiCN-containing layer, wherein the TiCN-containing layer is constituted by a TiC rich layer, a TiCN rich layer, and a TiN rich layer from the base material side . 5. The piezoelectric actuator according to claim 4 , wherein the TiCN-containing layer is formed by sequentially forming a TiC rich layer, a TiCN rich layer, and a TiN rich layer on a surface of an iron-based metal base material by a CVD method.

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